Surgical retractors for holding tissues at the edge of a surgical incision, or wound, away from the field of an operation have been in use for years. A halo style annular retractor is disclosed in the Budde U.S. Pat. No. 4,457,300, assigned to the assignee of the present invention. The retractor is comprised of a ring having a circumferential channel on the outside periphery of the ring. The channel is adapted to receive and support a retractor holder, which in turn supports a retractor blade or other tool. The retractor holder can be moved continuously through a 360.degree. path around the retractor ring.
In an embodiment disclosed in the Agbodoe, et al. U.S. Pat. No. 5,284,129, a halo style retractor is split into two semicircular ring sections which are pivotally connected together at their ends. One of the semicircular ring sections swivels with respect to the other ring section which is supported in a fixed position. The swiveling ring section is unlocked and relocked into a desired position by means of a screw clamp mechanism. The screw clamp mechanism may be disassembled to remove the swiveling ring section from the fixed ring section. The construction of the Agbodoe '129 reference has several disadvantages. First, the pivot joints at the ends of the ring sections interrupt the path of movement, and retractor holders cannot be positioned at or slid past the ends of the ring sections. Consequently, to move a retractor holder from one ring section to the other, the retractor holder must be physically removed from the one ring section and then remounted to the other ring section. That requirement has the disadvantages of consuming time during a surgical procedure, and of exposing the retractor to mishandling, being dropped, etc.
With the design in the Agbodoe '129 patent, the knob for locking the movable retractor in a particular position is located on the outer circumference of the retractor ring. In addition, the locking knobs on the retractor holders are also located on an outwardly directed surface of the retractor holders. Consequently, if the retractor holders are located at the ends of the semi-circular ring sections, the locking knob for the retractor holder is adjacent the locking knob for the retractor ring with the further disadvantage that there is interference in the manipulation and operation of either one of the two locking knobs.
The interruption of the circumferential retractor holder path by the pivot joints on opposing sides of the retractor ring results in the ring sections interfering with each other when one attempts to fold the moveable ring section up and over the fixed ring section. Therefore, in order to obtain greater access to the surgical field, the swiveling semicircular ring section must be disassembled and physically removed from the retractor. That process has the disadvantage of requiring surgical personnel to engage in a time-consuming disassembly process, and in addition, keep track of the loose parts which result from the disassembly process.